Taking an outside temperature is not as easy as you think it is. In order to get a proper reading, there are a few things to consider when using a thermometer.

“You want to have it not near another surface, like for example, if you have a thermometer right outside your house, especially on hot days it’s really going to be affected by the warm surface of the house and read artificially warm,” says Todd Foisy, the Science and Operations Officer at the National Weather Service in Caribou.

You also want to keep the thermometer out of direct sunlight. A thermometer in direct sunlight can read temps 20-30 above the actual temperature. Now there is a whole standardization of how you want weather equipment.

“Typically you want it five feet above the ground, and you want that ground to be a surface that’s typical for the area. So around here that might be grass. You don’t want it over concrete because that could have really bad affects on a sunny, warm day,” says Foisy.

You also don’t want the equipment near trees or houses or other structures. Also, a lot of weather equipment now will have little fans which keeps the air flowing. This doesn’t allow the air to become stagnant and warm. Now cars have sensors which tell you the outside temperature, and so do a lot of signs outside of businesses.

“A lot of bank thermometers and car thermometers the sensors are just by like a metal surface. And maybe you can get away with it when the temperature is like 60 or 70 degrees, and it’s not sunny. But when the sun comes out, that metal warms up and that thermometer is right next to the metal surface and it warms up also big time,” says Foisy.

You may notice that when you first turn on your car that has been sitting in the sun, the temp reads a lot warmer. Once you start driving and air flows through your car, the temperature will go down closer to normal.